[linux-lvm] snapshot pools, lvm roadmap
proclivity76 at yahoo.com
Fri Jan 7 19:01:56 UTC 2011
> I'm not sure what "Volume Shadow Copy" actually does, but we use DRBD (Data
> Replicating Block Device) to remotely mirror block devices - which could be
> marketed as "Volume Shadow Copy".
MS's VSS is their implementation of snapshots at the fs level. For instance,
you can set the C drive to back up to a D drive, allocating 80GB for all C drive
snapshots. Snapshots are removed automatically on a First-In, First-Out basis
as the storage ceiling is reached. Because the storage is shared, they can also
be deduplicated for speed and storage efficiency. Again, this has been in place
As I understand LVM now, each snapshot must have individual storage allocated.
When that ceiling is reached, the snapshot must still be manually removed.
Since snapshot storage can't be shared, copied blocks must be written to every
active snapshot, causing both a space and speed inefficiency.
I'm familiar with DRBD and have implemented it on HA systems. It's great, but
has nothing to do with the shared snapshots storage I desire for Linux.
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